Vista raises the bar for flaw finders

Microsoft launched its latest operating system - Windows Vista - on Monday, a move that will make finding easily exploitable vulnerabilities a lot harder, according to security researchers.

In a launch event in New York City, the software giant took the wraps off both Windows Vista and its Office 2007 productivity suite. Long awaited, Windows Vista brings together a number of security features, some aimed at hardening the operating system against attack and others designed to encourage users to make security a priority when using their PCs.

"None of the features in Windows Vista, either individually or together, are meant to be bulletproof," said Stephen Toulouse, senior product manager for Microsoft's Security Technology Unit. "But the defense-in-depth will significantly raise the security level compared to Windows XP."

The launch of its latest operating system comes five years after the company restructured its approach to software security with the Trustworthy Computing Initiative. The revamped strategy - prompted by the Code Red and Nimda worms that struck a massive number of the software giant's customers in the summer of 2001 - led to a massive push to educate developers and provide tools to weed out software bugs. In 2004, Microsoft refocused Windows XP Service Pack 2, making the update almost completely about security.

While other applications, including Internet Explorer 7 and Office 2007, have benefited from Microsoft's secure development lifecycle, the development of Windows Vista was the first time the software giant's consumer operating system was designed from the ground up with a focus on security. For example, the operating system enforces least-privilege rules of access, requesting the user's password to execute certain higher privilege tasks. The software giant has also improved the operating system's firewall and revamped the Security Centre to give more information to users. Internet Explorer 7 brings additional security enhancements, such as limiting ActiveX controls and significant anti-phishing features.

For security researchers, however, it's what's under the hood that matters. Three major features will make Vista more difficult to exploit even when vulnerabilities are found: Kernel Patch Protection, Data Execution Prevention, and Address Space Layout Randomisation.

The controversial Kernel Patch Protection, also known as PatchGuard, limits the practice of some software developers of creating add-on features for the operating system by patching the kernel, the core system software. Many security software makers have criticised the feature because it limits their software's ability to modify the core features offered by the Windows operating system.

"This is especially popular among anti-virus products, which sometimes use exactly the same hooking techniques as some popular malware, like rootkits," Joanna Rutkowska, senior researcher for COSEINC Advanced Malware Labs, said in an email interview with SecurityFocus. "This is not good, not only because it may have potential impact on system stability, but it also confuses malware detection tools."

Such restrictions are good for the overall security of the Windows platform, but it's not comprehensive by any means, Rutkowska said. PatchGuard only protects against modifications to code and static-kernel objects, what Rutkowska calls type-I infections. It does not detect modifications to dynamic structures (type-II infections) nor does it detect modifications to code running through hardware virtualisation (type-III infections), she said.

That's not surprising, because PatchGuard is not really about stopping malicious software from subverting the kernel, but preventing any software from destabilizing the system, said Ken Johnson, a software developer at remote-access provider Positive Networks.

"As far as I can tell, (PatchGuard) is a mechanism to force third-party driver (developers) to clean up their act and stop releasing poorly written drivers that destabilize customer computers and introduce security holes," Johnson said.

In a recent article in the technical publication Uninformed, Johnson - writing under the pseudonym "Skywing" - described several deficiencies in the latest version of PatchGuard, version 2. Microsoft programmers are currently studying the claims, said the software giant's Toulouse.

Other security technologies included in Microsoft's Windows Vista are not as controversial.

Address Space Layout Randomisation (ASLR), which makes it harder for an attacker to reliably run code that exploits remote memory flaws, has garnered the approval of many security researchers. Microsoft's implementation of the technique has some weaknesses, but overall the company has added a good foil to attacks that have plagued Microsoft's software in the past, said Positive Network's Johnson.

"Vista's ASLR is, on a whole, still a significant 'speed bump' that makes exploiting many vulnerabilities on Windows much more difficult to do reliably, especially in a 'fire and forget' fashion as typically used by worms," he said.

However, at least one other researcher has said the speed bump will not slow down the pace of exploits, because it can be circumvented.

"The ASLR implementation in Vista is not very resilient - it only randomizes the bases of certain system DLLs (dynamic link libraries) and not the rest of the loaded modules," Matthew Murphy, an application security engineer at Hypermedia Systems, stated in comments to a previous SecurityFocus article. "This means that today's attackers will still succeed tomorrow, because all they'll have to do is slightly tweak the jump points in their exploits."

Data Execution Prevention (DEP), a technology included in Windows XP Service Pack 2, monitors for attacks - or software bugs - that attempt to run code from a non-executable part of memory. While included in Windows XP SP2, the service is only activated by default on systems with 64-bit processors. With Windows Vista, Microsoft has set the technology to automatically monitor all essential Windows services.

Microsoft's Toulouse emphasised that Windows Vista is not the end of the software giant's fight to protect its customer from online threats.

"There are certain classes of attacks that we might see, after widespread deployment of Windows Vista, starting to go away, but none of this is to say that we can be complacent," Toulouse said. "We will still try to provide our users with tools that help them know what's going on their PC. And, we still urge customers that criminals are still out there, and you need to be cautious."